Sci Pharm www.scipharm.at Research article Open Access Anatomy of Subterranean Organs of Medicinally Used Cardueae and Related Species and its Value for Discrimination Elisabeth FRITZ *, Johannes SAUKEL Department of Pharmacognosy, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria * Corresponding author. E-mail: [email protected] (E. Fritz) Sci Pharm. 2011; 79: 157–174 doi:10.3797/scipharm.1010-05 Published: December 2nd 2010 Received: October 20th 2010 Accepted: December 2nd 2010 This article is available from: http://dx.doi.org/10.3797/scipharm.1010-05 © Fritz and Saukel et al.; licensee Österreichische Apotheker-Verlagsgesellschaft m. b. H., Vienna, Austria. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Numerous species of the Asteraceae, the composites, are famous for their use in both traditional and conventional medicine. Reliable anatomical descriptions of these plants and of possible adulterations provide a basis for fast identification and cheap purity controls of respective medicinal drugs by means of light microscopy. Nevertheless, detailed comparative studies on root and rhizome anatomy of valuable as well as related inconsiderable composite plants are largely missing yet. The presented study aims to narrow this gap by performing anatomical analyses of roots and rhizomes of 16 species belonging to the tribe Cardueae, of formerly and currently used drugs as well as their near relatives as potential adulterations (Carlina acaulis L., Carlina vulgaris L., Arctium lappa L., Arctium tomentosum Mill., Carduus defloratus L., Carduus personata (L.) Jacq, Cirsium arvense (L.) Scop., Cirsium vulgare (Savi) Ten., Cirsium erisithales (Jacq.) Scop., Onopordum acanthium L., Silybum marianum (L.) Gaertn., Rhaponticum scariosum Lam., Centaurea jacea L., Centaurea scabiosa L., Centaurea cyanus L., Cnicus benedictus L.). A detailed verbal and graphical survey of the analysed anatomical features is provided. Several characters were finally extracted which allow for discrimination of the examined species and may be effectively used for drug quality controls. Keywords Root anatomy • Asteraceae • Microscopy • Plant anatomy 158 E. Fritz and J. Saukel: Introduction The Asteraceae represent one of the largest plant families comprising at least 23,000 species and about 1,600 genera [1]. Numerous composites such as Carlina acaulis, Arctium lappa and Taraxacum officinale, to mention only a few, have a long history in both traditional and conventional medicine. Light microscopy is a common and effective method for the identification of pharmaceutically useful plants and their adulterations. Hence, detailed knowledge of the anatomy of the diverse plant parts used as drugs is required for quality control. Yet, reliable comparative studies of the anatomy of subterranean organs of medicinally exploited Asteraceae species and their close relatives are rare. Most studies date back to about 1900 and concentrate on the secretory system of the family tribes Cardueae (characterized by resin ducts) and Cichorieae (laticifers) in particular [2–5]. Most work, however, concerned the aerial vegetative organs and did not aim to discriminate species. Some recent studies deal with the subterranean organ anatomy of diverse Asteraceae species [e.g. 6–11]. However, the investigated species were of no medicinal value and not of a Western European origin. An additional recent study concentrates on the secretory structures of the subterranean organs of various species of the tribe Cardueae and demonstrated - based on five identified types of secretory ducts - the value of anatomical characters for the discrimination of composite plants [12]: • Secretory ducts of type SD1 and SD2a / SD2b are of schizogenous origin and distinguished based on the C1:C2-quotient (i.e. the length of the cells lining the ducts [C1] divided by the length of adjacent cells [C2], longitudinal section, see fig. 1 [fig cited: 12]). Fig. 1. Secretory duct in longitudinal section build from two adjacent layers of cells differing in length. The quotient C1:C2 is used to discriminate between three types of secretory ducts (fig. cited: [12]). • Secretory ducts of type SD3 show cell lysis: the large lumen is filled with the remnants of the cells. • Secretory ducts of type SD4 seem to be actually intercellular space, filled with diverse substances secreted by the adjacent parenchyma cells. Sci Pharm. 2011; 79: 157–174 Root anatomy of Cardueae 159 Although the secretory system proofed valuable for species discrimination, the anatomy of entire roots and rhizomes is still insufficiently described. So far a single study only focuses on medicinal drugs [13] by comparing the root anatomy of Taraxacum spp., Leontodon sp., Aposeris foetida, and Hypochaeris sp.. In order to narrow this gap of knowledge, a comprehensive study on the anatomy of the subterranean organs of 32 genera and 57 species from the tribes Cardueae (22 species) and Cichorieae (35 species) used in medicine or occurring as potential adulterations was initiated. The anatomy of these plants was analysed in detail and a database of typical anatomical features created [14]. The present work deals with the tribe Cardueae and analyses the underground part anatomy of species possessing a taproot or dominating rhizome. Taxa with a fibrous root system were excluded. The focus thereby lies on formerly or currently medicinally used species of the Cardueae, which have been used for medical purposes since long: Thus already Hieronymus Bock [15] mentions Carlina acaulis L. as a plant highly valued by people as a diaphoretic and diuretic medicine and against worms. The roots soaked in vinegar were also known as appropriate remedy against scabies and tetter [16]. Today, this plant is still used in traditional medicine and serves as an ingredient of various liquids such as Swedish bitters elixir, as a diuretic as well as a stomachic remedy and against skin diseases [17, 18]. Even though rarely used nowadays, another species of the genus Carlina, Carlina vulgaris L., still has a place in traditional medicine. The species is applied against nocturnal enuresis and to cure frightened babies [19]. The medicinally use of Arctium lappa L. reaches back to the ancient times. Dioskurides [20] praises the effects of its roots as an expectorans (the antitussive activity was confirmed by Kardošová [21]) and its application on luxations and sprains. Lonicerus [22] mentions its effects against asthma. The usage of A. lappa oil as hair restorer was first mentioned in 1673 [Pankovius, 1673 in: 23] and is still popular among people. In traditional medicine, A. lappa – along with Arctium tomentosum Mill. – is still valued as a plant with antirheumatic, diuretic and diaphoretic effects [17, 19]. Recent studies document a gastroprotective activity [24] and hepatoprotective effects [25]. Although officinal in former times (Radix et Herba Spinae albae seu Cardui tomentosi; [23]), these days, Onopordum acanthium is no longer used except in anthroposophical medicine (Onopordi acanthi herba) [17]. The roots (together with the sap of the fresh leaves) were reported to be useful against stiff neck and opisthotonus [26, 20] and as a diaphoretic and laxative remedy [23]. Rhaponticum has been used in Chinese, Tibetan and Mongol medicine for more than 5,000 years [27]. Rhaponticum carthamoides (Willd.) Iljin. was studied currently as it is supposed to possess various positive effects on memory, blood, cardiovascular and nervous system and on physiological functions such as work capacity and sexual function (reviewed by Kokoska [28]). Łotocka & Geszprych [27] dealt with the anatomy and secretory structures of R. carthamoides but the identification of the plant and its roots remained problematic as comparative material from other species of the genus is missing. Sci Pharm. 2011; 79: 157–174 160 E. Fritz and J. Saukel: On that account the anatomy of Rhaponticum scariosum Lam. – the only species of the genus native to Austria (the area mainly addressed here) – has been included in our studies. Though R. scariosum has been used in former times as substitute to Rheum palmatum [29] it is not applied any longer. Carduus defloratus L., Carduus personata (L.) Jacq, Cirsium arvense (L.) Scop., Cirsium vulgare (Savi) Ten., Cirsium erisithales (Jacq.) Scop. Silybum marianum L., Centaurea jacea L., Centaurea scabiosa L., Centaurea cyanus and Cnicus benedictus L. have been examined as near relatives of the taxa mentioned above. Results Reliable anatomical root and rhizome characters discriminating between the various species investigated in this study were identified. These features are proofed valuable for the characterisation of the drugs and may be used for quality control: The following main anatomical features of roots and rhizomes can be used for purity and quality control in pharmacy: the overall distribution and proportions of the principal tissues in transverse section, the fine structure of the cork, vessel types, the occurrence of fibers including their maximum diameter and wall structure, and, finally, the occurrence of sclereids and secretory ducts in diverse tissues. Our studies demonstrated that even within one single plant the diameter of the largest vessels may differ largely depending on their position along the root axis.